Not many years ago the solid state electronics manufacturing industry was a fraction of the size that it is at present notwithstanding the development of integrated circuits and transistors. However, since the development of miniaturization of integrated circuits in the form of semiconductor chips, there has been enormous growth in this industry. At the same time, mass production techniques have been increasingly applied in the manufacturing and assembly of electronics apparatus to reduce costs and increase output.
It is well known in the electronics trade that the assembly of printed circuit boards, commonly termed PC boards, that the thickness of the PC boards vary, and that the components that are installed into PC boards such as integrated circuit sockets, resistors, capacitors, transistors and the like are all manufactured with random length electrical conductors commonly referred to as leads or pins. These pins are plugged into holes that are designed into the PC board which holes contain in their inside diameter other conductors connected to the printed circuit on the PC board. When the pins are plugged into the holes in the PC board, they are soldered in place, thereby establishing permanent electrical communication between the lead or pin of the component and the correspondent portion of the printed circuit. Since the manufacturing specifications provide that the pins only extend through the PC board a particular distance, random length pins that exceed the specification have to be trimmed.
This is frequently accomplished in facilities that utilize mass production techniques with automatic or semi-automatic trimming and forming equipment that may utilize solenoids, pneumatic cylinders for movement and placement of the cutting apparatus, etc. Alternatively, the trimming and forming device can be manually operated, particularly in locations where electrical wiring and/or pneumatic air lines are cumbersome to arrange or the power sources are inaccessible. Similarly, in non-automated operations such as the assembly of low-volume items or, more particularly, prototypes (often called "breadboarding"), the use of manually operated tools to trim and form the leads of these components represents the only practical approach.
A substantial amount of inventive activity has been devoted to the design of such manually operated tools. Though various names are utilized for such tools, examples of patents that have been granted on such devices include those disclosed by Smith, U.S. Pat. Nos. 4,271,593; Burns, 3,333,338; Halstead, et al., 3,337,953; and Weissman, et al., 3,370,353. It will be seen from these disclosures that such devices have usually been designed with handles that move the cutting surfaces thereof about a single axis in the manner of a pliers, sometimes with spring means to open the handles thereof when pressure is not being applied. Such devices normally contain a plurality of holes in a blade or jaw into which a plurality of leads can be inserted for simultaneous trimming. Indeed, similar apparatus has been invented in the form of a hand shear for opening dispensing cartridges, as disclosed by Kurtz, U.S. Pat. No. 4,158,914. In addition, in some of the foregoing references, interchangeable dies or spacers can be inserted into the disclosed tools whereby predetermined lengths of the leads remain after trimming has been accomplished.
One definite disadvantage of all of these inventions is a consequence of the pivoting motion between the blades or cutting surfaces, i.e., the plurality of leads being trimmed and formed are not all cut at the same angle for a fixed orientation of the component to which the leads are attached. This is because the pivoting or rotational motion of such devices necessarily result in a different cutting angle for each lead because the dies are incapable of trimming all of the leads at the same distance from the axis of rotation of the tool. What results is non-uniformity in the manner in which the leads are trimmed. This difficulty is aggravated by the varying force required as the cutting surfaces or blades pass through their operative arc, because it is in the nature of the geometry of such devices that multiple leads have to be cut at the same moment in certain positions and no leads are cut at certain other positions.
The present inventor has determined that these difficulties may be overcome utilizing linear rather than pivoting or rotational motion between the cutting surfaces. Moreover, the use of linear motion between the cutting surfaces in combination with staggered positioning of the holes in the die can provide for only one lead at a time in a perfectly sequenced succession leading to substantially consistent force that is applied to the cutting surfaces to accomplish trimming of each lead in a uniform manner.